1. Field of the Invention
The invention relates to a fastening system and to a fastening of a rail on a substrate. The system comprises in this case in general form the components required for fastening the rail, whereas the fastening of the rail relates to the specific assembly of the rail, such as is provided under practical conditions.
2. Description of the Related Art
Fastening systems and fastenings of this type are described for example in German patent application publication DE 33 24 225 A1 or German utility model DE 201 22 524 U1. They serve in particular to support a rail on what is known as a fixed substrate. Fixed substrates of this type are also referred to as a “slab track” and have, in contrast to a superstructure formed from loose ballast, no inherent resilience. The fixed substrate itself can in this case be formed for example by concrete slabs, on which the rails are directly assembled, or by sleepers which are likewise made of solid material, such as concrete.
In particular when the fastening system comprises sleepers which form the substrate on which the rails are to be fastened, lateral stop shoulders are generally moulded onto these sleepers. The stop shoulders delimit on the one hand, laterally between themselves, an aperture in which the rail and the components required for fastening thereof sit. On the other hand, the shoulders serve as stops against which the guide plates, which are intended for laterally guiding the rail in question, are supported.
Suitable fastening elements, generally screws, are used to fix these guide plates either directly to the fixed substrate or the respective sleeper or to fix them to the substrate via interposed components, such as force distribution plates. Conventionally, the fastening elements additionally serve to tension spring elements which exert a holding force, which is directed in the direction of the fixed substrate, onto the rail foot. Depending on the shaping of the substrate and the fastening means used, additional underlay and fastening means are required to correctly orient and hold the rails.
The known fastening systems ensure secure holding of the rails of a track body even under very high loads such as occur during high-speed operation. Owing to the large number of elements required for each individual fastening point, the costs for manufacturing and assembling a fastening system of this type are however considerable.
The large number of constructional elements which are required, in conventional fastening systems of the type described hereinbefore, for fastening the rail on a fixed track also lead to exact setting of the rail gauge being able to be brought about only with great difficulty. Such settings of the track can be required owing to insufficient precision of the concrete sleepers generally used for supporting the rails or variations in the dimensions of other fastening and support elements. Likewise, it can be necessary, in sections of track subjected to particularly high loads, to readjust after a specific operating time the spacing, forming the rail gauge, of the rails of the respective track body.
In DE 33 24 225 A1, which was mentioned at the outset, or German utility model DE 201 22 524 U1, which has also been mentioned hereinbefore, it has been proposed to provide, for compensating for production tolerances and for exact setting of the rail gauge, a support element which is arranged between the guide plate and the stop which accommodates the lateral forces occurring as a vehicle travels over the rail during practical operation. This support element is in this case embodied in a wedge-shaped manner in such a way that, as a result of displacement of the support element, the guide plate is moved more or less intensively in a direction directed transversely to the longitudinal extension of the rail. In order to prevent accidental displacement of the support element as a consequence of the lateral forces occurring during practical operation, the support element and the guide plate are in this case each provided with projections and recesses via which the guide plates are coupled to the respective support element in a form-fitting manner. Under normal operating conditions, the forces transmitted by the guide plate via this form-fitting connection are sufficient to hold the support element in its position by self-locking.
Nevertheless, correct functioning of the known fastening systems, which are suitable for compensating for production tolerances in the manner described hereinbefore, requires these systems to be assembled and maintained with great care and precision. Practical experience has shown that these requirements often cannot be met owing to the available staff being insufficiently qualified, inadequate assembly technology or harsh weather conditions. In such cases, it can occur, despite all preventative design measures, that the connection of the support element and guide plate becomes detached as a consequence of incorrect assembly or wear and the support element moves automatically out of its correct position.
A change in the position of the support element has been found to be particularly problematic when the rail is mounted on a resilient pad. Pads of this type are used to impart to the respective fastening point defined resilience in the direction of gravity as a rail vehicle travels over the rail. This resilience greatly lengthens the service life of the rail. However, the movement is accompanied by a movement also of all other elements of the fastening system. An imprecise, loosely positioned support element increases the play with which this movement can be carried out and thus causes as a result increasing wear.